1. Field of the Invention
This invention relates to a disk recording playback for recording and playing back data on and from disks such as video disks, digital audio disks, optical disks and magnetic disks.
2. Background of the Invention
Optical disks capable of recording and playing back data at high density are gaining widespread acceptance. Such a disk has spiral tracks (or guide tracks) formed thereon. Address data is recorded in positions throughout the disk so that the data may be recorded on and played back from the set position of the track. When the desired address is designated, the conversion means (reading or writing head) for recording and playing back data on and from the disk is driven (tentatively sent) to the desired address and, on reaching a position at least close to the designated address, it sequentially traces the tracks one after another or jumps over several tracks at a time (precisely sent) to gain access to the designated address.
When the head is first tentatively to a position close to the desired address, the actual position must be first read to determine the direction of and the distance to the designated address. In case the presently - positioned address is unavailable for a certain reason, the head is conventionally made to trace tracks until the actual address becomes readable or it is tentatively sent in a fixed direction to allow it to read out another address located close to a new position. In the case of track tracing, it takes a long time until the actual position is read if there is a relatively large dropout near the actual position, whereas in the case of the fixed displacement, it may read out an address whose position is shifted relatively far from the initial position.